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For the vulcanization of polyisoprene, compute the weight percent of sulfur that must be added to ensure that \(10 \%\) of possible sites will be crosslinked; assume that, on the average, 3.5 sulfur atoms are associated with each crosslink.

Demonstrate, in a manner similar to Equation \(15.4,\) how vulcanization may occur in a chloroprene rubber.

Name the following polymer(s) that would be suitable for the fabrication of cups to contain hot coffee: polyethylene, polypropylene, poly(vinyl chloride), PET polyester, and polycarbonate. Why?

For each of the following pairs of polymers do the following: (1) state whether or not it is possible to determine whether one polymer has a higher melting temperature than the other; (2) if it is possible, note which has the higher melting temperature and then cite reason(s) for your choice; and (3) if it is not possible to decide, then state why. (a) Branched polyethylene having a numberaverage molecular weight of \(850,000 \mathrm{g} / \mathrm{mol}\); linear polyethylene having a number-average molecular weight of \(850,000 \mathrm{g} / \mathrm{mol}\) (b) Polytetrafluoroethylene having a density of \(2.14 \mathrm{g} / \mathrm{cm}^{3}\) and a weight-average molecular weight of \(600,000 \mathrm{g} / \mathrm{mol}\); PTFE having a density of \(2.20 \mathrm{g} / \mathrm{cm}^{3}\) and a weight-average molecular weight of \(600,000 \mathrm{g} / \mathrm{mol}\) (c) Linear and syndiotactic poly(vinyl chloride ) having a number-average molecular weight of \(500,000 \mathrm{g} / \mathrm{mol} ;\) linear polyethylene having a number-average molecular weight of \(225,000 \mathrm{g} / \mathrm{mol}\) (d) Linear and syndiotactic polypropylene having a weight-average molecular weight of 500,000 g/mol; linear and atactic polypropylene having a weight- average molecular weight of \(750,000 \mathrm{g} / \mathrm{mol}\)

Briefly explain the difference in molecular chemistry between silicone polymers and other polymeric materials.

List two important characteristics for polymers that are to be used in fiber applications

Cite five important characteristics for polymers that are to be used in thin- film applications.

Cite the primary differences between addition and condensation polymerization techniques.

Nylon 6,6 may be formed by means of a condensation polymerization reaction in which hexamethylene diamine \(\left[\mathrm{NH}_{2}-\left(\mathrm{CH}_{2}\right)_{6}-\right.\) \(\left.\mathrm{NH}_{2}\right]\) and adipic acid react with one another with the formation of water as a byproduct. What masses of hexamethylene diamine and adipic acid are necessary to yield \(20 \mathrm{kg}\) of completely linear nylon \(6,6 ?\) (Note: the chemical equation for this reaction is the answer to Concept Check \(15.12 .\) )

What is the distinction between dye and pigment colorants?